274 PHYSIOLOGY OF BACTERIA 



when they are dead. The bread yeast industry has made 

 use of this fact for determining the dead cells in a batch 

 of bread yeast, by suspending the cells in a counting 

 chamber filled with a very dilute solution of methylene 

 blue (Lafar V, 173). Fulmer and Buchanan (1923) 

 applied this method to measure quantitatively the 

 number of dead cells in a yeast culture exposed to some 

 disinfectant. 



In using this method, it should be borne in mind that 

 it means a new definition of death. Considering the 

 death process as a continuous curve plotted against time, 

 the point where the protoplasm begins to take the dye 

 is probably not identical with the point where the faculty 

 of reproduction is lost. 



Generally speaking, bacteria are too small to lend 

 themselves to the staining technique. This applies 

 also to most other methods for proving the death of cells 

 in botanical or zoological experiments, such as plas- 

 molytic reaction, loss of motility, response to stimuli, 

 etc. The inaccuracy of the various staining methods 

 has been pointed out by Bickert (1930). 



III. THE LOGARITHMIC ORDER OF DEATH 



(a) ORDER OF DEATH OF HIGHER ORGANISMS 



When large organisms, such as green plants, or 

 vertebrates, or insects, are exposed to a detrimental 

 influence, some time will pass before the first organism 

 dies. They will not all die at the same moment; some 

 will die soon, others will be more resistant. The order 

 of death will be represented by a chance curve, due 

 to the variation of resistance among the individuals. 

 This can be shown by the order of death of seeds, or of 

 fruit flies exposed to high temperatures. Table 76 



